git-mergetool--lib.sh: add error message if 'setup_user_tool' fails

In git-mergetool--lib.sh::setup_tool, we check if the given tool is a
known builtin tool, a known variant, or a user-defined tool by calling
setup_user_tool, and we return with the exit code from setup_user_tool
if it was called. setup_user_tool checks if {diff,merge}tool.$tool.cmd
is set and quietly returns with an error if not.

This leads to the following invocation quietly failing:

	git mergetool --tool=unknown

which is not very user-friendly. Adjust setup_tool to output an error
message before returning if setup_user_tool returned with an error.

Note that we do not check the result of the second call to
setup_user_tool in setup_tool, as this call is only meant to allow users
to redefine 'cmd' for a builtin tool; it is not an error if they have
not done so.

Note that this behaviour of quietly failing is a regression dating back
to de8dafbada (mergetool: break setup_tool out into separate
initialization function, 2021-02-09), as before this commit an unknown
mergetool would be diagnosed in get_merge_tool_path when called from
run_merge_tool.

Signed-off-by: Philippe Blain <levraiphilippeblain@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/git-mergetool--lib.sh b/git-mergetool--lib.sh
index 269a60ea44c4a6dd83c123a94a1d6617059fbd01..d7e410d94814497d3e9428117f983a0b2f14458e 100644 (file)
--- a/git-mergetool--lib.sh
+++ b/git-mergetool--lib.sh
@@ -159,7 +159,7 @@ check_unchanged () {
 }
 
 valid_tool () {
-       setup_tool "$1" && return 0
+       setup_tool "$1" 2>/dev/null && return 0
        cmd=$(get_merge_tool_cmd "$1")
        test -n "$cmd"
 }
@@ -250,7 +250,12 @@ setup_tool () {
                . "$MERGE_TOOLS_DIR/${tool%[0-9]}"
        else
                setup_user_tool
-               return $?
+               rc=$?
+               if test $rc -ne 0
+               then
+                       echo >&2 "error: ${TOOL_MODE}tool.$tool.cmd not set for tool '$tool'"
+               fi
+               return $rc
        fi
 
        # Now let the user override the default command for the tool.  If

diff --git a/t/t7610-mergetool.sh b/t/t7610-mergetool.sh
index 5c5e79e99052c324fcf47556174045e6d7af3c91..4ec11f997e79d37e958167c8c3a68074e47a39b6 100755 (executable)
--- a/t/t7610-mergetool.sh
+++ b/t/t7610-mergetool.sh
@@ -899,4 +899,12 @@ test_expect_success 'mergetool with guiDefault' '
        git commit -m "branch1 resolved with mergetool"
 '
 
+test_expect_success 'mergetool with non-existent tool' '
+       test_when_finished "git reset --hard" &&
+       git checkout -b test$test_count branch1 &&
+       test_must_fail git merge main &&
+       yes "" | test_must_fail git mergetool --tool=absent >out 2>&1 &&
+       test_grep "mergetool.absent.cmd not set for tool" out
+'
+
 test_done